Montreal Ice Age Caves discovered under Saint-Leonard park

The Pie-XII Park in central Montréal is already well-known for a subterranean secret, with an entrance way for the St. Léonard cave that people can go down and explore. But it was what lay hidden beyond this section that stunned speleologists. Two cavers discovered an entirely new network of shafts and tunnels that reached almost 213 meters (700 feet) deep into the rock.

The two who made the remarkable find, Daniel Caron and Luc Le Blanc, finally entered the new system this October, but their hunch for the new caves occurred way back in 2014. After a year of exploring the already mapped sections of St. Léonard’s caverns, they came across a narrow opening in the rock at the back of one of the cavities. Too small for a person to slide through, a camera revealed it to open out into a new chamber beyond.

It was not until this year that they have been able to chisel away enough rock to allow them to slip into the system and start exploring. From the large hollow they passed into, the cavers then dropped down into a narrow hallway perhaps 6 meters (20 feet) high. “The walls are perfectly smooth and the ceiling is perfectly horizontal,” Le Blanc told National Geographic.

The cave systems in this part of the world are thought to have been formed when the great ice sheet that once stretched across much of North America eventually retreated around 12,000 years ago. As the glaciers receded over the land, fissures were formed in the ground beneath, leading to the system that is now seen hidden under Montréal.

One of the most incredible parts of this recent discovery is that even though St. Léonard cave was first found in 1812, and utility pipes and basements have been built since then as the city continued to expand, this latest system still somehow remained undetected until now. They think this is probably because the caves are too deep underground for anyone to have noticed before.

The tunnels likely extend right down to the water table underneath the city. However, the team have halted exploring it further due to the large amounts of water filling the lower sections of the cave. They plan to return next year to see if they can go any deeper.